Motivation
The epoll transport was updated in #7834 to decouple setting of the
timerFd from the event loop, so that scheduling delayed tasks does not
require waking up epoll_wait. To achieve this, new overridable hooks
were added in the AbstractScheduledEventExecutor and
SingleThreadEventExecutor superclasses.
However, the minimumDelayScheduledTaskRemoved hook has no current
purpose and I can't envisage a _practical_ need for it. Removing
it would reduce complexity and avoid supporting this specific
API indefinitely. We can add something similar later if needed
but the opposite is not true.
There also isn't a _nice_ way to use the abstractions for
wakeup-avoidance optimizations in other EventLoops that don't have a
decoupled timer.
This PR replaces executeScheduledRunnable and
wakesUpForScheduledRunnable
with two new methods before/afterFutureTaskScheduled that have slightly
different semantics:
- They only apply to additions; given the current internals there's no
practical use for removals
- They allow per-submission wakeup decisions via a boolean return val,
which makes them easier to exploit from other existing EL impls (e.g.
NIO/KQueue)
- They are subjectively "cleaner", taking just the deadline parameter
and not exposing Runnables
- For current EL/queue impls, only the "after" hook is really needed,
but specialized blocking queue impls can conditionally wake on task
submission (I have one lined up)
Also included are further optimization/simplification/fixes to the
timerFd manipulation logic.
Modifications
- Remove AbstractScheduledEventExecutor#minimumDelayScheduledTaskRemoved()
and supporting methods
- Uplift NonWakeupRunnable and corresponding default wakesUpForTask()
impl from SingleThreadEventLoop to SingleThreadEventExecutor
- Change executeScheduledRunnable() to be package-private, and have a
final impl in SingleThreadEventExecutor which triggers new overridable
hooks before/afterFutureTaskScheduled()
- Remove unnecessary use of bookend tasks while draining the task queue
- Use new hooks to add simpler wake-up avoidance optimization to
NioEventLoop (primarily to demonstrate utility/simplicity)
- Reinstate removed EpollTest class
In EpollEventLoop:
- Refactor to use only the new afterFutureTaskScheduled() hook for
updating timerFd
- Fix setTimerFd race condition using a monitor
- Set nextDeadlineNanos to a negative value while the EL is awake and
use this to block timer changes from outside the EL. Restore the
known-set value prior to sleeping, updating timerFd first if necessary
- Don't read from timerFd when processing expiry event
Result
- Cleaner API for integrating with different EL/queue timing impls
- Fixed race condition to avoid missing scheduled wakeups
- Eliminate unnecessary timerFd updates while EL is awake, and
unnecessary expired timerFd reads
- Avoid unnecessary scheduled-task wakeups when using NIO transport
I did not yet further explore the suggestion of using
TFD_TIMER_ABSTIME for the timerFd.
Motivation:
In AbstractBoostrap, options and attrs are LinkedHashMap that are synchronized on for every read, copy/clone, write operation.
When a lot of connections are triggered concurrently on the same bootstrap instance, the synchronized blocks lead to contention, Netty IO threads get blocked, and performance may be severely degraded.
Modifications:
Use ConcurrentHashMap
Result:
Less contention. Fixes https://github.com/netty/netty/issues/9426
Motivation:
EPOLL supports decoupling the timed wakeup mechanism from the selector call. The EPOLL transport takes advantage of this in order to offer more fine grained timer resolution. However we are current calling timerfd_settime on each call to epoll_wait and this is expensive. We don't have to re-arm the timer on every call to epoll_wait and instead only have to arm the timer when a task is scheduled with an earlier expiration than any other existing scheduled task.
Modifications:
- Before scheduled tasks are added to the task queue, we determine if the new
duration is the soonest to expire, and if so update with timerfd_settime. We
also drain all the tasks at the end of the event loop to make sure we service
any expired tasks and get an accurate next time delay.
- EpollEventLoop maintains a volatile variable which represents the next deadline to expire. This variable is modified inside the event loop thread (before calling epoll_wait) and out side the event loop thread (immediately to ensure proper wakeup time).
- Execute the task queue before the schedule task priority queue. This means we
may delay the processing of scheduled tasks but it ensures we transfer all
pending tasks from the task queue to the scheduled priority queue to run the
soonest to expire scheduled task first.
- Deprecate IORatio on EpollEventLoop, and drain the executor and scheduled queue on each event loop wakeup. Coupling the amount of time we are allowed to drain the executor queue to a proportion of time we process inbound IO may lead to unbounded queue sizes and unpredictable latency.
Result:
Fixes https://github.com/netty/netty/issues/7829
- In most cases this results in less calls to timerfd_settime
- Less event loop wakeups just to check for scheduled tasks executed outside the event loop
- More predictable executor queue and scheduled task queue draining
- More accurate and responsive scheduled task execution
Motivation:
Look like `EmbeddedChannelPipeline` should also override `onUnhandledInboundMessage(ChannelHandlerContext ctx, Object msg)` in order to do not print "Discarded message pipeline" because in case of `EmbeddedChannelPipeline` discarding actually not happens.
This fixes next warning in the latest netty version with websocket and `WebSocketServerCompressionHandler`:
```
13:36:36.231 DEBUG- Decoding WebSocket Frame opCode=2
13:36:36.231 DEBUG- Decoding WebSocket Frame length=5
13:36:36.231 DEBUG- Discarded message pipeline : [JdkZlibDecoder#0, DefaultChannelPipeline$TailContext#0]. Channel : [id: 0xembedded, L:embedded - R:embedded].
```
Modification:
Override correct method
Result:
Follow up fix after https://github.com/netty/netty/pull/9286
Motivation:
On servers with many pipelines or dynamic pipelines, it is easy for end user to make mistake during pipeline configuration. Current message:
`Discarded inbound message PooledUnsafeDirectByteBuf(ridx: 0, widx: 2, cap: 2) that reached at the tail of the pipeline. Please check your pipeline configuration.`
Is not always meaningful and doesn't allow to find the wrong pipeline quickly.
Modification:
Added additional log placeholder that identifies pipeline handlers and channel info. This will allow for the end users quickly find the problem pipeline.
Result:
Meaningful warning when the message reaches the end of the pipeline. Fixes#7285
Motivation:
We observed some test-failues sometimes in the CI which happened if sc.close() was not completed before the next test did run. If this happened we would fail the bind(...) as the LocalAddress was still in use.
Modifications:
Await the close before return
Result:
Fixes race in testsuite which resulted in FixedChannelPoolTest.testAcquireNewConnection to fail if FixedChannelPoolTest.testCloseAsync() did run before it.
Motivation:
Currently GraalVM substrate returns null for reflective calls if the reflection access is not declared up front.
A change introduced in Netty 4.1.35 results in needing to register every Netty handler for reflection. This complicates matters as it is difficult to know all the possible handlers that need to be registered.
Modification:
This change adds a simple
null check such that Netty does not break on GraalVM substrate without the reflection information registration.
Result:
Fixes#9278
Motivation:
c9aaa93d83 added the ability to specify an EventLoopTaskQueueFactory but did place it under MultithreadEventLoopGroup while not really belongs there.
Modifications:
Make EventLoopTaskQueueFactory a top-level interface
Result:
More logical code layout.
Motivation:
Sometimes it is desirable to be able to use a different Queue implementation for the EventLoop of a Channel. This is currently not possible without resort to reflection.
Modifications:
- Add a new constructor to Nio|Epoll|KQueueEventLoopGroup which allows to specify a factory which is used to create the task queue. This was the user can override the default implementation.
- Add test
Result:
Be able to change Queue that is used for the EventLoop.
Motivation:
In the current implementation, the synchronous close() method for FixedChannelPool returns
after scheduling the channels to close via a single threaded executor asynchronously. Closing a channel
requires event loop group, however, there might be a scenario when the application has closed
the event loop group after the sync close() completes. In this scenario an exception is thrown
(event loop rejected the execution) when the single threaded executor tries to close the channel.
Modifications:
Complete the close function only after all the channels have been close and introduce
closeAsync() method for cases when the current/existing behaviour is desired.
Result:
Close function would completely when the channels have been closed
Motivation:
Sometimes it is beneficial to be able to set a parent Channel in EmbeddedChannel if the handler that should be tested depend on the parent.
Modifications:
- Add another constructor which allows to specify a parent
- Add unit tests
Result:
Fixes https://github.com/netty/netty/issues/9228.
Motivation:
When Netty is run through ProGuard, seemingly unused methods are removed. This breaks reflection, making the Handler skipping throw a reflective error.
Modification:
If a method is seemingly absent, just disable the optimization.
Result:
Dealing with ProGuard sucks infinitesimally less.
Motivation:
When initializing the AnnotatedSocketException in AbstractChannel, both
the cause and the stack trace are set, leaving a trailing "Caused By"
that is compressed when printing the trace.
Modification:
Don't include the stack trace in the exception, but leave it in the cause.
Result:
Clearer stack trace
Motivation:
OOME is occurred by increasing suppressedExceptions because other libraries call Throwable#addSuppressed. As we have no control over what other libraries do we need to ensure this can not lead to OOME.
Modifications:
Only use static instances of the Exceptions if we can either dissable addSuppressed or we run on java6.
Result:
Not possible to OOME because of addSuppressed. Fixes https://github.com/netty/netty/issues/9151.
Motivation:
Clean the code , replace all logic that checks Null with the ObjectUtil utility class in bootstrap package
Modification:
Replace all logic that checks null with the ObjectUtil utility class
Result:
Less verbose code.
Motivation:
SimpleChannelPool provides ability to provide custom callbacks/handlers
on major events such as "channel acquired", "channel created" and
"channel released". In the current implementation, when a request to
acquire a channel is made for the first time, the internal channel pool
creates the channel lazily. This triggers the "channel created" callback
but does not invoke the "channel acquired" callback. This is contrary to
caller expectations who assumes that "channel acquired" will be invoked
at the end of every successful acquire call. It also leads to an
inconsistent API experience where the acquired callback is sometimes
invoked and sometimes it isn't depending on wheather the internal
mechanism is creating a new channel or re-using an existing one.
Modifications:
Invoke acquired callback consistenly even when creating a new channel
and modify the tests to support this behaviour
Result:
Consistent experience for the caller of acquire API. Every time they
call the API, the acquired callback will be invoked.
Motivation:
GraalVM native images are a new way to deliver java applications. Netty is one of the most popular libraries however there are a few limitations that make it impossible to use with native images out of the box. Adding a few metadata (in specific modules will allow the compilation to success and produce working binaries)
Modification:
Added properties files in `META-INF` and substitutions classes (under `internal.svm`) will solve the compilation issues. The substitutions classes are not visible and do not have a public constructor so they are not visible to end users.
Result:
Fixes#8959
This fix is very conservative as it applies the minimum config required to build:
* pure netty servers
* vert.x applications
* grpc applications
The build is having trouble due to checkstyle which does not seem to be able to find the copyright notice on property files.
Motivation
The optimization in #8988 didn't correctly handle the specific case
where the channel hasDisconnect == false, and a
ChannelOutboundHandlerAdapter subclass overrides only the close(ctx,
promise) method without also overriding the disconnect(ctx, promise)
method.
Modifications
Adjust AbstractChannelHandler.disconnect(...) method to divert to
close(...) in !hasDisconnect case before computing target context for
the event.
Result
Fixes#9092
Motivation:
When a Channel was closed its isActive() method must return false.
Modifications:
First check for isOpen() before isBound() as isBound() will continue to return true even after the underyling fd was closed.
Result:
Fixes https://github.com/netty/netty/issues/9026.
Motivation:
IdleStateHandler may trigger unexpected idle events when flushing large entries to slow clients.
Modification:
In netty design, we check the identity hash code and total pending write bytes of the current flush entry to determine whether there is a change in output. But if a large entry has been flushing slowly (for some reason, the network speed is slow, or the client processing speed is too slow to cause the TCP sliding window to be zero), the total pending write bytes size and identity hash code would remain unchanged.
Avoid this issue by adding checks for the current entry flush progress.
Result:
Fixes#8912 .
Motivation:
Invoking ChannelHandlers is not free and can result in some overhead when the ChannelPipeline becomes very long. This is especially true if most handlers will just forward the call to the next handler in the pipeline. When the user extends Channel*HandlerAdapter we can easily detect if can just skip the handler and invoke the next handler in the pipeline directly. This reduce the overhead of dispatch but also reduce the call-stack in many cases.
This backports https://github.com/netty/netty/pull/8723 and https://github.com/netty/netty/pull/8987 to 4.1
Modifications:
Detect if we can skip the handler when walking the pipeline.
Result:
Reduce overhead for long pipelines.
Benchmark (extraHandlers) Mode Cnt Score Error Units
DefaultChannelPipelineBenchmark.propagateEventOld 4 thrpt 10 267313.031 ± 9131.140 ops/s
DefaultChannelPipelineBenchmark.propagateEvent 4 thrpt 10 824825.673 ± 12727.594 ops/s
Motivation:
Deprecate ChannelOption.newInstance(...) as it is not used.
Modifications:
Deprecate ChannelOption.newInstance(...) as valueOf(...) should be used as a replacement.
Result:
Fixes https://github.com/netty/netty/issues/8983.
Motivation:
0a0da67f43 introduced a testcase which is flacky. We need to fix it and enable it again.
Modifications:
Mark flaky test as ignore.
Result:
No flaky build anymore.
Motivation:
https://github.com/netty/netty/pull/8826 added @Deprecated to the exceptionCaught(...) method but we missed to add @SupressWarnings(...) to it's sub-types. Beside this we can make the deprecated docs a bit more clear.
Modifications:
- Add @SupressWarnings("deprecated")
- Clarify docs.
Result:
Less warnings and more clear deprecated docs.
Motivation:
Systems depending on Netty may benefit (telemetry, alternative even loop scheduling algorithms) from knowing the number of channels assigned to each EventLoop.
Modification:
Expose the number of channels registered in the EventLoop via SingleThreadEventLoop.registeredChannels.
Result:
Fixes#8276.
Motivation:
It appears this was an oversight, maybe was valid at some point in the past. Noticed while reviewing #8958.
Modifications:
Change AbstractChannelHandlerContext to not extend DefaultAttributeMap.
Result:
Simpler hierarchy, eliminate unused attributes field from each context instance.
Motivation:
PromiseCombiner is not thread-safe and even assumes all added Futures are using the same EventExecutor. This is kind of fragile as we do not enforce this. We need to enforce this contract to ensure it's safe to use and easy to spot concurrency problems.
Modifications:
- Add new contructor to PromiseCombiner that takes an EventExecutor and deprecate the old non-arg constructor.
- Check if methods are called from within the EventExecutor thread and if not fail
- Correctly dispatch on the right EventExecutor if the Future uses a different EventExecutor to eliminate concurrency issues.
Result:
More safe use of PromiseCombiner + enforce correct usage / contract.
Motivation:
`DefaultFileRegion.transferTo` will return 0 all the time when we request more data then the actual file size. This may result in a busy spin while processing the fileregion during writes.
Modifications:
- If we wrote 0 bytes check if the underlying file size is smaller then the requested count and if so throw an IOException
- Add DefaultFileRegionTest
- Add a test to the testsuite
Result:
Fixes https://github.com/netty/netty/issues/8868.
Motivation:
To make it easier to understand why a Channel was closed previously and so why the operation failed with a ClosedChannelException we should include the original Exception.
Modifications:
- Store the original exception that lead to the closed Channel and include it in the ClosedChannelException that is used to fail the operation.
- Add unit test
Result:
Fixes https://github.com/netty/netty/issues/8862.
Motivation:
41e03adf24 marked ChannelHandler.exceptionCaught(...) as @deprecated but missed to also mark ChannelHandlerAdapter.exceptionCaught(...) as @deprecated. We should do so as most people extend the base classes and not implement the interfaces directly.
Modifications:
Mark ChannelHandlerAdapter.exceptionCaught(...) as @deprecated as well.
Result:
Mark method as @deprecated to warn users about its removal.
Motivation:
We have a utility method to check for > 0 and >0 arguments. We should use it.
Modification:
use checkPositive/checkPositiveOrZero instead of if statement.
Result:
Re-use utility method.
Motivation:
We cache the Runnable for some tasks to reduce GC pressure in 4 different fields. This gives overhead in terms of memory usage in all cases, even if we always execute in the EventExecutor (which is the case most of the times).
Modifications:
Move the 4 fields to another class and only have one reference to this in AbstractChannelHandlerContext. This gives a small overhead in the case of execution that is done outside of the EventExecutor but reduce memory footprint in the more likily execution case.
Result:
Less memory used per AbstractChannelHandlerContext in most cases.
Motivation:
We need to update to a new checkstyle plugin to allow the usage of lambdas.
Modifications:
- Update to new plugin version.
- Fix checkstyle problems.
Result:
Be able to use checkstyle plugin which supports new Java syntax.
Motivation:
We need to release the message when we throw an IllegalArgumentException because of a validation failure of the promise to eliminate the risk of a memory leak.
Modifications:
- Consistently release the message before rethrow
- Add testcase.
Result:
Fixes https://github.com/netty/netty/issues/8765.
